In a UMTS (Universal Mobile Telecommunications System) network, for the purposes of improving spectral efficiency and improving data rates, system features based on W-CDMA (Wideband Code Division Multiple Access) are maximized by adopting HSDPA (High Speed Downlink Packet Access) and HSUPA (High Speed Uplink Packet Access). For this UMTS network, for the purposes of further increasing high-speed data rates, providing low delay and so on, long-term evolution (LTE) has been under study (non-patent literature 1). Unlike W-CDMA, LTE uses, as multiplexing schemes, OFDMA (Orthogonal Frequency Division Multiple Access) on downlink channels (downlink) and SC-FDMA (Single Carrier Frequency Division Multiple Access) on uplink channels (uplink).
In the third-generation mobile communication system, it is possible to achieve a transmission rate of maximum approximately 2 Mbps on the downlink by using a fixed band of approximately 5 MHz. Meanwhile, in the LTE system, it is possible to achieve a transmission rate of about maximum 300 Mbps on the downlink and about 75 Mbps on the uplink by using a variable band which ranges from 1.4 MHz to 20 MHz. Furthermore, in the UMTS network, for the purpose of achieving further broadbandization and higher speed, successor systems of LTE have been under study (for example, LTE-Advanced (LTE-A)). In LTE-A (LTE Release 10), a heterogeneous network (HetNet), which places significance on the local area environment, in addition to the conventional cellular environment, is under study.